1. Field of the Invention
This invention relates to a dynamical quantity sensor for detecting a dynamical quantity such as an angular velocity, acceleration, or the like.
2. Description of the Related Art
A tuning fork type device or a tuning plate type device using a piezoelectric device has been known in the past as a device for detecting a yaw rate by utilizing the Coriolis force.
However, such a device requires machining of a complicated shape and bonding of a piezoelectric device, and is not therefore free from the problems that the reduction of size and cost of production and accomplishment of higher precision are difficult. A yaw rate sensor according to the prior art comprises piezoelectric ceramics, for example, and detects the yaw rate by utilizing the Coriolis force, but has been difficult to reduce size and the cost of production. To solve these problems, the inventors of the present invention have already proposed a yaw rate sensor having the construction which is shown in FIG. 1 of the accompanying drawings. In this construction, a vibrating direction 10 of a weight 1, a rotating direction 11 to be applied to the sensor and a detecting direction 4 of the Coriolis force obtained by such a rotation have a relationship such that they orthogonally cross one another.
On the other hand, the sensor device 1 must be vibrated in the vibrating direction 10 of the weight and the detecting direction 4 of the Coriolis force. Therefore, the sensor device 1 (that is, the weight) is constituted in such a manner that a supporting direction (the direction of the arrangement of a support member 2) coincides with a direction of the axis of rotation 7. In this construction, an electrode 6 for detecting the vibration must be disposed on a plane below the sensor device 1 opposing the first plane 8 of the sensor device. Accordingly, there remain the problems yet to be solved that the construction is complicated and the production is difficult.
It may be conceivable to form the second surface 9 of the sensor device 1 on the upper surface thereof but in such a case, the support member 2 must be disposed at a lower portion. In view of the production of the sensor device by micro-machining, however, it is quite impossible to accomplish the production method of such a sensor device.
It is therefore an object of the present invention to provide a dynamical quantity sensor having a novel structure which can be easily produced by micro-machining owing to its simple shape, and makes it possible to reduce size and the cost of production, and to accomplish higher precision.
To accomplish the object described above, the present invention provides a dynamical quantity sensor fundamentally comprising a weight, anchor portions, connecting portions for connecting the weight and the anchor portions, and peripheral members encompassing the members described above, wherein the members other than the peripheral members are integrally shaped by the same semiconductor material. The upper main planes of these members are mutually disposed on the same plane, the anchor portions and the peripheral members are fixed to a substrate, and the weight can move in a first direction and in a second direction orthogonally crossing the first direction inside a plane in parallel with the plane described above.
More specifically, the first embodiment of the present invention provides a dynamical quantity sensor wherein a weight is supported by L-shaped beams, a plane defined by these L-shaped beams is used as a moving plane of the weight, and the movement of the weight due to the function of a dynamical quantity is detected.
The second embodiment of the present invention provides a dynamical quantity sensor wherein first beams are extended from anchor portions, a movable intermediate support member is disposed on the first beams, second beams extending in a direction crossing substantially orthogonally the first beams are disposed on the intermediate support member, a weight is disposed on the second beams, and the movement of the weight resulting from a dynamical quantity is detected.
In the present invention, the weight is allowed to move with deformation of the L-shaped beams. The movement of the weight resulting from the action of a dynamical quantity is detected, and the dynamical quantity is detected.
The weight is allowed to move due to deformation of the first beams or the second beams. The movement of the weight with the dynamical quantity is detected, and the dynamical quantity is detected.